The use of \link{exovar}{exercises with variations} can effectively stop copying between students (if the variations are sufficiently effective), because each student has his/her own exercise.

What will really happen in such cases is that discussion and mutual help will develop among the students, with more advanced students helping less advanced, often by explaining the method to solve the exercise. Sometimes the help will take the form of a direct hands-on, and it is the physical presence of the teacher in the computer room which can dissuade such kinds of `help'. 